External preparations containing an adrenocortical hormone have so far been used widely in the treatment of dermatoses, in particular intractable dermatoses such as a topic dermatitis and contact dermatitis and it is known that they have high pharmacological effects (Gekkan Yakuji (Pharmaceuticals Monthly); 26, 8, 55, 1984). Japanese Kokai Publication Sho-62-149620, for instance, discloses an external preparation containing an adrenocortical hormone as a principal active component.
However, adrenocortial hormone-containing external preparations may possibly induce adverse effects at the sites of application, for example increased easy infectivity, skin thinning, vascular wall embrittlement and abnormal activation of the pilosebaceous system and, in addition, the drug substances endermically absorbed may possibly produce systemic adverse effects. Thus, the closest attention should be paid to their doses. Therefore, for hydrocortisone acetate, for instance, which is a typical adrenocortical hormone, the Japanese Pharmacopoeia prescribes an upper limit use concentration of about 1% by weight and, for dexamethasone and prednisolone, an upper limit concentration of about 0.1 to 0.5% by weight.
On the other hand, external preparations with reduced adverse effects are also available, for example external preparations containing a nonsteroidal antiinflammatory agent and/or an antihistaminic agent. However, as compared with adrenocortical hormone-containing ones, they are much less effective against such intractable dermatoses as mentioned above (Shinyaku to Chiryo (New Remedies and Therapy); 25, 298, 41, 1984).
As mentioned above, adrenocortical hormones have high pharmacological effects but are disadvantageous in that they have strong side effects. Therefore, it is earnestly desired that preparations with which clinical effects comparable to those attained with the conventional preparations can be produced at lower adrenocortical hormone concentrations be developed. In the state of the art, even if higher clinical effects are required, it is impossible to increase their contents to levels exceeding those currently employed, when their side effects are taken into consideration.
For solving these problems, Japanese Kokai Publication Sho-61-40210 discloses a preparation for treating dermatoses and skin protection which comprises vitamin E and Japanese Kokai Publication Sho-53-136521 discloses a preparation for the treatment of vegetating dermatoses which contains .alpha.-tocopherol. However, these are insufficiently effective in intractable dermatoses possibly due to the low concentration of vitamin E or .alpha.-tocopherol in the preparations.
Japanese Kokai Publication Hei-06-179619 discloses an external preparation for the treatment of dermatoses which contains vitamin E and a transdermal absorption enhancer. However, when it is administered continuedly for achieving satisfactory therapeutic effects, the transdermal absorption enhancer may possibly produce skin irritating effects.
Furthermore, Japanese Kokai Publication Hei-06-247852 discloses an external preparation for the treatment of dermatoses which contains 1 to 30% by weight of vitamin E and 1 to 30% by weight of squalene. It is known that this vitamin E- and squalene-containing external preparation for treating dermatoses can be widely applied to dermatoses without producing such adverse effects as encountered with the steroid-containing preparations mentioned above. However, for producing higher clinical effects, preparations showing still stronger effects are desired.